The present invention relates to knock-down boat structures, and more particularly to an assemblable boat formed of roll-up panel elements and associated structural components.
High performance, lightweight personal watercraft have enjoyed a renaissance in recent years, primarily due to the advent of kayaks for white water use, as well as river and ocean-going kayaks. In addition, small personal boats continue to be used for hunting and fishing, as well as wilderness travel on waterways and lakes. Although such watercraft are well designed for use on water, they are often difficult to transport by vehicle, due to their size factors, particularly length.
As a result, there is a strong need and desire for watercraft that can be reiteratively disassembled for transport in small packages and reassembled for use in the field. The simplest of such boats are inflatables, which rely on pneumatic tubes not only to create positive buoyancy, but also to provide rigidity, structural shape, and resistance to impact with obstacles. However, inflatables are generally low performance craft, due to the shape limitations imposed by the pneumatic tubes. Moreover, pressure loss can be catastrophic, even with the provision of compartmentalized pneumatic chambers.
Another class of knock-down watercraft is the folding boat, which is generally comprised of an expandable internal frame that supports a removable flexible outer skin defining the hull and deck. Often the outer skin is a durable waterproof fabric stretched taut over the internal frame to define a streamlined shape that is more efficient than most inflatable craft. One problem associated with this construction is that assembly of the complex frame structure can be a difficult process.
Another common problem involves the assembly of separate panels to form the outer skin. If the panels are joined permanently, and folded along the joining seam, there is a concentration of wear and stress along the seam that can result in leaks and structural failure. This difficulty may be exacerbated if the folded panel construction is then rolled or folded across the joining seam. On the other hand, if the panels are joined temporarily and designed to be separable, it is necessary to provide a mechanism for joining the panels along generally long seams that is reliable and reusable. Moreover, the mechanism must provide both a waterproof seal and a strong mechanical bond, as the boat relies on tension in the outer skin to define the hull shape. In the prior art, waterproof zippers used for this purpose have been the locus of minor failures such as leakage and major failures such as catastrophic separation of the panels.
Regarding the panels that define the hull and deck of the watercraft, every design requires a compromise between providing a frame that minimizes unsupported spans of the outer skin, and providing a hull material that is sufficiently stiff to maintain its shape yet sufficiently flexible for folding. A more extensive frame involves added weight and complexity in assembly, whereas heavier hull materials are more difficult to fold and limit the compactness of the knock-down state of the watercraft. A possible solution to this design dilemma is to provide removable stiffeners or stays to strengthen the hull panels, as long as these components do not add to the difficulty in boat assembly.